There are available to the consumer an ever-increasing number of portable battery operated devices, and those devices create an ever-increasing demand for batteries to serve as power sources. Conventionally, primary batteries such as carbon-zinc or alkaline batteries have been used as power sources, but since these primary batteries are typically not designed for recharging, the consumer is forced to continue purchasing new batteries as the old ones are drained.
Secondary batteries such as nickel-cadmium batteries are available which can repeatedly be recharged and reused for significant number of charge/discharge cycles. Such secondary batteries may be made with terminals and case configurations identical to primary batteries so as to be useable in the relatively large number of devices designed for primary batteries. In addition, such secondary batteries can also be associated with battery chargers useful in recharging the secondary batteries. Providing chargers for such secondary batteries creates the opportunity for insertion of primary batteries, having the same size and shape configuration, into the charger by an unwary consumer, even though such primary batteries are not intended to be recharged. It has been found that many carbon-zinc and alkaline primary batteries, if subjected to charging current, will eventually release electrolyte which can corrode and damage the surrounding energy-using device. Charging of such primary batteries may also produce other adverse effects.
In prior art approaches, in order to provide for charging of nickel-cadmium batteries while avoiding the adverse effects associated with recharging primary batteries, the nickel-cadmium batteries have been made of special size or shape to distinguish them from the non-rechargeable or primary batteries so that only the rechargeable battery will physically fit into a charger for recharging. Other prior art approaches have provided the rechargeable battery with a third contact terminal (in addition to the two contact terminals used to discharge energy from the battery) which is used to charge the battery. A non-rechargeable battery not having the third charging contact terminal cannot be charged in the charger. Another prior art approach provides for the insertion of a uni-directional current flow device into the non-rechargeable battery so that current may flow from the battery during discharge but cannot flow through the battery in the reverse direction during charging. Each of these prior art approaches has not proved to be entirely satisfactory at least for the reason that they each involve additional or special parts or components and hence increase the cost of the battery.